There is a technology that extracts numerical values from a text file that is targeted for compression and that compresses the extracted numerical values in units of numerals. In this technology, a compressed code is allocated to each of the numerals from 0 to 9 and then each of the numerals included in the numerical values extracted from the text file that is targeted for the compression is converted into a compressed code. Furthermore, by adding, to the converted compressed code, for example, a code indicating information related to a numerical value, such as specifying of a full width or a half width, the presence or absence of a comma, the presence or absence of a decimal point, the number of significant numerals, or the like, the numerical value is converted into a compressed code.
Patent Document 1: International Publication Pamphlet No. WO 2008/047432
Patent Document 2: Japanese Laid-open Patent Publication No. 2013-150041
Patent Document 3: Japanese Laid-open Patent Publication No. 05-174064
However, if numerical values are compressed in units of numerals, compressed codes associated with the numerals are needed by the same number of digits of the numerals; therefore, the length of compressed codes of the overall numerical values is increased. Consequently, in some cases, the compression ratio may be decreased.